Plasma membrane in eukaryotes is composed of phospholipid bilayer where phospholipids are distributed asymmetrically. Phosphatidylserine having an amino group is located in the inside part of the membrane (the inner leaflet) and not in the outside part of the membrane (the outer leaflet). The asymmetrical distribution of phosphatidylserine is considered to be maintained by the action of an enzyme flippase which transports aminophospholipids toward cytoplasmic side of plasma membrane. In contrast, in apoptotic cells, the asymmetrical distribution of phosphatidylserine is disrupted, and phosphatidylserine is no longer confined to the inner leaflet, but is allowed to be exposed on the cell surface. Phagocytes are considered to recognize phosphatidylserine exposed on apoptotic cells and engulf the cells specifically rather than viable cells. However, molecular mechanism is unknown responsible for the asymmetrical membrane distribution of phosphatidylserine in viable cells and the surface exposure of phosphatidylserine in apoptotic cells. Also, it has not been known whether apoptotic cells can induce their engulfment by phagocytes solely by the surface exposure of phosphatidylserine.